Many bicycle riders may frequently wish to use a bag alternatively as a pannier or as a knapsack. For example, touring cyclists may wish to carry the pannier as a knapsack while hiking in areas that are accessible only on foot or while simply taking a stroll off the bicycle. Also, students who ride a bicycle to and from school may wish to use a bag as a pannier while riding, and then as a knapsack while at school.
The prior art includes many bag constructions which are adapted for attachment to a bicycle.
One such bag is described in U.S. Pat. No. 3,938,716. This patent describes a bag which can be carried on a user's back using shoulder straps, or which alternatively can be secured to a side of a bicycle luggage carrier. A principal disadvantage of this design is that the bag is secured to the bicycle vertically on one side or the other of one of the wheels, thus displacing the center gravity of the bicycle. This can present difficulty to the rider of the bicycle and could lead to an accident. Furthermore, such "saddle bags" increase the aerodynamic drag of the bicycle, and access to the contents of the bag from the top of the bag while it is still attached to the side of the carrier is difficult since the contents are piled up inside the bag.
Another type of backpack for attachment to a bicycle is described in U.S. Pat. No. 4,491,258. This bag includes a main storage element having three compartments. When secured to a luggage carrier on a bicycle, the three compartments form two saddle bags, which hang vertically on either side of the wheel, and a central compartment which sits on top of the luggage carrier. The central compartment is illustrated as a small cylindrical bag resting on top of the luggage carrier. While this bag does not create an imbalance on the bicycle to which it is secured, it still has the disadvantages of increasing the aerodynamic drag and making access to the contents of the compartments difficult while the bag is supported on the bicycle. Furthermore, a principal disadvantage is that it requires a back-pack having three compartments. Therefore, this back-pack is relatively complicated to manufacture and involves a complicated series of steps to be secured to a bicycle. In addition, the contents of the back pack must be divided up between the three smaller compartments. Another disadvantage of this design is that it requires that the shoulder strap assembly be removed in order to secure it to a luggage carrier.
Yet another bag is described in U.S. Pat. No. 4,059,207. It describes a bag adapted for attachment to the substantially horizontal surface of a motorcycle gas tank. While this bag provides a single compartment and does not create an imbalance, it does have other disadvantages. It requires that a pad be installed between the gas tank and the bag in order to support the bag evenly and horizontally on the gas tank. This bag is only appropriate for motorcycles having large support surfaces, such as gas tanks. As with the design referred to in the previous example, the support surface underneath the bag, in this case the pad, is the same size as the bottom of the bag and the bag is a conventional construction bag.
There is a need for a bicycle mounted knapsack which provides a convenient single compartment easily accessible while mounted to the bicycle and is easily attached to a luggage carrier centrally on the bicycle in a way that does not significantly increase aerodynamic drag.